There is interest in the dairy and juice industry to combine milk and juice to form a stable, good-tasting beverage. The stability and good taste are the two biggest barriers to overcome. The current stability problem is the precipitation or curdling of milk proteins when the composition is below the isoelectric point of all such proteins.
There are several methods used to prepare milk/juice drinks at a pH around pH 4. These methods usually use sour milk or fermented milk (acidic milk) rather then sweet milk (natural pH of 6.4 to 6.7) for the drinks. There is also a series of patents teaching the addition of gum as thickeners and/or the process to stabilize the milk/juice drinks. (e.g., U.S. Pat. No. 3,625,702; U.S. Pat. No. 3,996,390; U.S. Pat. No. 4,031,264; U.S. Pat. No. 4,046,925; and U.S. Pat. No. 4,212,893).
A different approach is the removal of the cations and anions from milk and juice (see U.S. Pat. No. 4,676,988). The components, milk and juice, are prepared by cation exchange followed by anion exchange. After blending of the separately prepared ingredients, the blend is essentially homogenized and then optionally pasteurized or sterilized and/or carbonated to prepare the beverage.
U.S. Pat. Nos. 3,764,710 and 4,061,792 teach how to make stable beverages by removing the pectic substances and tannin from fruits or fruits extract. This was done by the addition of an acidified solution of proteins which coagulate, and by treating the juice with pectinase. The acidified milk is added to yield a sour juice-milk beverage.
European patent 0,083,327 described a milk/juice beverage with no need for any type of stabilizing agent and teaches the invention concerning hydrolysis of pure lactose into glucose and galactose, which are free from salts. Glucose and galactose actually acts as a binder of the proteins. The beverage can be stored for several weeks to several months.